Population inversion and gain calculations for 4p⁵4d-4p⁵5p and 4p⁵5s - 4p⁵5p Kr-like transitions in Y IV, Zr V, Nb VI and Mo VII

We present calculations of the quasi-steady state gain coefficient for the 4p⁵4d ¹P-4p⁵5p 1/2[1/2]₀ transition in Kr-like Y IV, Zr V, Nb VI and Mo VII ions. Gain coefficients which can lead to FUV-VUV (∼260 to 60 nm) lasing are found in all ions. Large gain coefficients are found for each ion at temperatures in excess of the ion's equilibrium temperature; realizing lasing in these systems will require a transient excitation mechanism. The density at which the maximal gain coefficient obtains increases for increasing ionization state. The 4p⁵5s 1/2[1/2]₁-4p⁵5p 1/2[1/2]₀ and 4p⁵5s 3/2[3/2]₁-4p⁵5p 1/2[1/2]₀ transitions also show population inversion and modest gain coefficients. Attractive features of these ions as potential lasents are the large ratio between the energy of the lasing transition and the excitation energy of the upper level of the lasing transition as well as the ease with which they are produced in a low temperature, table-top scale plasma source.